Rep. Chris Van Hollen on Tuesday won his contentious fight over Rep. Donna Edwards in Maryland’s Democratic Senate primary, all but guaranteeing that he will replace retiring Sen. Barbara A. Mikulski next year.

Katie McGinty won the Pennsylvania Democratic Senate primary, besting former Rep. Joe Sestak in a race that saw her benefit from the enormous support of the party establishment — including crucial endorsement from President Barack Obama and Vice President Joseph R. Biden Jr.

Democratic voters on Tuesday will decide the party’s nominees for Senate in Maryland and Pennsylvania, two races that have featured hard-fought battles between candidates split along establishment, gender and — at least in Maryland’s case — racial lines.

In both contests, a late front-runner has emerged: The most recent polls show former Clinton administration official Katie McGinty and Rep. Chris Van Hollen with leads over their foremost opponents, onetime Rep. Joe Sestak and Rep. Donna Edwards, respectively. Both are backed by much of the Democratic Party establishment -- support that has given them a financial edge in the elections’ final weeks.

Portman has $13.5 million in cash on hand. (Tom Williams/CQ Roll Call)

With Senate primaries underway, many candidates are touting their fundraising prowess ahead of the general election to show they have the resources to win.

Several Republicans who won their seats in the 2010 GOP wave now have to defend them in a presidential year, when Democrats tend to have higher turnout. Some of these candidates have posted strong numbers, but a couple of Democratic challengers also pulled in impressive hauls.

Candidate for U.S. Senate Katie McGinty, D-Pa., in west Philadelphia with other local Democrats. ( Bill Clark/CQ Roll Call)

PHILADELPHIA – West Philadelphia is not where Katie McGinty was born and raised. But the candidate carrying the hopes and dreams of Democratic leaders brought her campaign to this predominantly African-American community this week, picking a busy intersection on a sunny afternoon to shake hands and take pictures.

“She’s the lady who’s never shady. First name Katie!” said Manwell “The Voice” Glenn, a local party operative who spoke rhymes into a bullhorn as he introduced McGinty to the men and women walking past. “McGinty is in the building, ladies and gentlemen!”

The Democratic Senatorial Campaign's independent expenditure arm will spend $1.1 million on TV ads in Pennsylvania to back Senate candidate Katie McGinty, according to a source tracking the buy.

The ads will begin running statewide on Tuesday, April 12 and run through the end of the primary, on April 26, according to four sources with knowledge of the buy. The ads will run on broadcast and cable.

The Democratic Senatorial Campaign Committee is spending $425,000 on TV ads to boost Pennsylvania Senate candidate Katie McGinty, according to an official with the committee. That's a decision that will aid the establishment-backed candidate ahead of her April 26 primary, but one that could draw criticism the party is siphoning valuable resources better used in a general election.

The money will replace the McGinty campaign's own TV ad reservations statewide starting Tuesday, according to the DSCC official and two sources tracking the ad buy.

Democratic leaders have taken an unusually aggressive approach to the party’s Senate primaries this year, offering key endorsements in competitive races where, in some cases, voters are split. Amid an anti-establishment mood, their overt involvement carries risk — though the tactic has seemed effective, so far.

The latest example came Wednesday in Pennsylvania, where President Barack Obama and Vice President Joseph R. Biden Jr. endorsed Katie McGinty in her bid for Senate, passing over her opponent, former Rep. Joe Sestak. Last week, the Democratic Senatorial Campaign Committee announced its formal support of McGinty, a former Al Gore adviser, who polls show trails Sestak but has earned the support of many Pennsylvania Democratic leaders, including Gov. Tom Wolf and Sen. Bob Casey.